Making no attempt to feign democracy, citizens have had to rely on leaked draft texts to get just a partial glimpse of what is in the extensive agreement. Once the negotiators have come to a deal, democratic deliberation will be further subverted by “fast-tracking” the TPP, putting it to Congress for a yes/no vote with no amendments and limited debate. Depending on what happens in Hawaii this week, a Congressional vote could happen as soon as November 1st.

The TPP is one of three major international treaties — also including the TTIP Atlantic-version and TISA services agreement — currently under negotiation. These treaties aim to lock-in policies that make it easier for the most dominant corporations and banks to rake in profits, and harder for people and democratic governments to decide their own fate. It amounts to more regulation and bureaucracy facilitating the profits and property rights of the mega-rich, and less protections for workers, indigenous rights, farmers, health, the environment, and smaller businesses.

Like NAFTA and other (misleadingly described) “free-trade agreements,” the TPP would pit workers of different countries against one another and drive down wages and living standards. Richard Trumka, President of AFL-CIO, the largest federation of unions in the United States, recently told the Guardian that never before have unions been so unified in opposing something. Describing general effects on U.S. jobs and the economy, Trumka said:

“It doesn’t affect just people in manufacturing…It affects everybody, including people in services. When high wages are driven down in manufacturing and elsewhere, it affects everyone in the community. When a manufacturing plant moves out — and we’ve lost tens of thousands of them since 2000 — it affects everybody. It hurts the wage base and tax base.”

Leaked texts from the TPP indicate that not only does it extend the NAFTA-like regime, but it goes well beyond it. Investor rights provisions in the TPP empower corporations to bypass domestic courts and sue governments in international tribunals for imagined losses of “expected profits” — for example, over gold still in the ground.

Currently these “investor-state” systems are being used by corporations to sue over denial of mining permits, pollution cleanup requirements, minimum wage law, climate regulations, cigarette health labels, and a long list of other public interest policies.

For Hawaii, aspects of the TPP might be likened to an international level PLDC—on steroids. Corporate profit protections would be privileged over Hawaii’s unique protections for conservation lands and publicly managed resources.

Development companies would acquire strengthened legal rights to maximize their private investments using public resources. These legal rights can create a “chilling effect,” whereby governments hesitate to pass regulations that might interrupt or irritate private investors.

All of this is of particular concern in regards to ongoing violations of Kānaka rights to manage and access resources and sacred places, and potentially of concern to unresolved seized Crown and Government land issues.

Indigenous communities globally are calling the TPP / TTIP a new wave of colonization—treaties being made without their participation or consent, but with extensive impacts on their lands and the appropriation and privatization of their cultures and knowledges. It should not be ignored that TPP negotiations are being “hosted” by the U.S. in Hawaii, amidst de-colonial and de-occupation struggles.

While seemingly disparate, these things are tied together by an underlying agenda to extend the profits, powers, privatization rights, markets and speculative capacities of the world’s largest corporations and banks, while shredding what remains of the social safety net and public protections.

TPP has an underlying agenda to extend the profits, powers, privatization rights, markets and speculative capacities of the world’s largest corporations and banks, while shredding what remains of the social safety net and public protections.

These are not just matters of “corporate greed” (though that is part)—they are the drives of a system that is structured by compulsive commodification and profit maximization. In recent decades, neoliberal ideology has imposed extremes of this capitalist logic.

While it comes cloaked in rhetoric of freedom, in truth all that comes “free” are the profits of those with the power to enclose the commons, speculate on non-existent abstractions (wreaking hunger and homelessness), and sue citizens for attempting to govern their own lives.

The decades-long corporate power grab and assault on people, democracy and earth also has a counter—the global movement of movements that is rising to make a fairer, more ecologically sane, and more cooperative and compassionate global future. What brings us together is our love for the planet, our respect for and responsibility to one another, and our belief that a better world is possible.

While today many of us focus on stopping the TPP, these efforts are about the equality, democracy, human solidarity, justice, and true freedom that we seek to build.

Organizers and movements on Maui, in solidarity with people around the world, have called for a “convergence by land and sea to stop the TPP” on July 29 in Lahaina, where negotiations are taking place. Organizer Trinette Furtado says that all are invited that afternoon to a collective blowing of the conch shell: “The conch shell (or pū, in ‘ōlelo Hawaii) was included because it calls for a cessation of time; of people.

Because it demands attention and asks all to bear witness. We are sounding a call to attention; a call to stand and join together.”

For those that choose to visit the TPP negotiations, please be very respectful of place, take out everything you bring in, and use busses and parking shuttles if possible. Kamaʻaina of Lahaina did not invite the TPP negotiations, nor should they have to deal with any kind of pilikia or ʻōpala left behind.

In line with the Hawaiian wisdom “I ka wā ma mua, ka wā ma hope” (the future is in the past), it is worth recalling that July 31 also marks Lā Hoʻihoʻi Ea, which was celebrated as Hawaiian national independence during much of the 19th century.

On this “Restoration day” in 1843, after the islands were temporarily claimed by a rogue British captain, Hawaiian emissaries secured sovereignty and Kamehameha III famously proclaimed, “ua mau ke ea o ka ‘āina i ka pono”—“the sovereignty of the land continues through justice and proper acts” (translation by Noelani Goodyear-Ka‘opua in A Nation Rising).

Grounded in knowledge of histories past, we might ask what history is being made today, and how we will participate in shaping the future.

Let's take a moment to recap the argument of the last two posts here on The Archdruid Report before we follow it through to its conclusion. There are any number of ways to sort out the diversity of human social forms, but one significant division lies between those societies that don’t concentrate population, wealth, and power in urban centers, and those that do.

One important difference between the societies that fall into these two categories is that urbanized societies—we may as well call these by the time-honored term “civilizations”—reliably crash and burn after a lifespan of roughly a thousand years, while societies that lack cities have no such fixed lifespans and can last for much longer without going through the cycle of rise and fall, punctuated by dark ages, that defines the history of civilizations.

It’s probably necessary to pause here and clear up what seems to be a common misunderstanding. To say that societies in the first category can last for much more than a thousand years doesn’t mean that all of them do this.

I mention this because I fielded a flurry of comments from people who pointed to a few examples of societies without cities that collapsed in less than a millennium, and insisted that this somehow disproved my hypothesis.

Not so; if everyone who takes a certain diet pill, let’s say, suffers from heart damage, the fact that some people who don’t take the diet pill suffer heart damage from other causes doesn’t absolve the diet pill of responsibility.

In the same way, the fact that civilizations such as Egypt and China have managed to pull themselves together after a dark age and rebuild a new version of their former civilization doesn’t erase the fact of the collapse and the dark age that followed it.

The question is why civilizations crash and burn so reliably. There are plenty of good reasons why this might happen, and it’s entirely possible that several of them are responsible; the collapse of civilization could be an overdetermined process.

Like the victim in the cheap mystery novel who was shot, stabbed, strangled, clubbed over the head, and then chucked out a twentieth floor window, that is, civilizations that fall may have more causes of death than were actually necessary.

The ecological costs of building and maintaining cities, for example, place much greater strains on the local environment than the less costly and concentrated settlement patterns of nonurban societies, and the rising maintenance costs of capital—the driving force behind the theory of catabolic collapse I’ve proposed elsewhere—can spin out of control much more easily in an urban setting than elsewhere. Other examples of the vulnerability of urbanized societies can easily be worked out by those who wish to do so.

That said, there’s at least one other factor at work.

As noted in last week’s post, civilizations by and large don’t have to be dragged down the slope of decline and fall; instead, they take that route with yells of triumph, convinced that the road to ruin will infallibly lead them to heaven on earth, and attempts to turn them aside from that trajectory typically get reactions ranging from blank incomprehension to furious anger.

It’s not just the elites who fall into this sort of self-destructive groupthink, either: it’s not hard to find, in a falling civilization, people who claim to disagree with the ideology that’s driving the collapse, but people who take their disagreement to the point of making choices that differ from those of their more orthodox neighbors are much scarcer.

They do exist; every civilization breeds them, but they make up a very small fraction of the population, and they generally exist on the fringes of society, despised and condemned by all those right-thinking people whose words and actions help drive the accelerating process of decline and fall.

The next question, then, is how civilizations get caught in that sort of groupthink. My proposal, as sketched out last week, is that the culprit is a rarely noticed side effect of urban life.

People who live in a mostly natural environment—and by this I mean merely an environment in which most things are put there by nonhuman processes rather than by human action—have to deal constantly with the inevitable mismatches between the mental models of the universe they carry in their heads and the universe that actually surrounds them.

People who live in a mostly artificial environment—an environment in which most things were made and arranged by human action—don’t have to deal with this anything like so often, because an artificial environment embodies the ideas of the people who constructed and arranged it. A natural environment therefore applies negative or, as it’s also called, corrective feedback to human models of the way things are, while an artificial environment applies positive feedback—the sort of thing people usually mean when they talk about a feedback loop.

This explains, incidentally, one of the other common differences between civilizations and other kinds of human society: the pace of change. Anthropologists not so long ago used to insist that what they liked to call “primitive societies”—that is, societies that have relatively simple technologies and no cities—were stuck in some kind of changeless stasis.

That was nonsense, but the thin basis in fact that was used to justify the nonsense was simply that the pace of change in low-tech, non-urban societies, when they’re left to their own devices, tends to be fairly sedate, and usually happens over a time scale of generations.

Urban societies, on the other hand, change quickly, and the pace of change tends to accelerate over time: a dead giveaway that a positive feedback loop is at work.

Notice that what’s fed back to the minds of civilized people by their artificial environment isn’t simply human thinking in general. It’s whatever particular set of mental models and habits of thought happen to be most popular in their civilization.

That obsession, and the models and mental habits that unfold from it, have given us an urban environment full of straight lines, simple geometrical shapes, hard boundaries, and clear distinctions—and thus reinforce our unthinking assumption that these things are normal and natural, which by and large they aren’t.

Modern industrial civilization is also obsessed with the frankly rather weird belief that growth for its own sake is a good thing. (Outside of a few specific cases, that is. I’ve wondered at times whether the deeply neurotic American attitude toward body weight comes from the conflict between current fashions in body shape and the growth-is-good mania of the rest of our culture; if bigger is better, why isn’t a big belly better than a small one?)

In a modern urban American environment, it’s easy to believe that growth is good, since that claim is endlessly rehashed whenever some new megawhatsit replaces something of merely human scale, and since so many of the costs of malignant growth get hauled out of sight and dumped on somebody else.

In settlement patterns that haven’t been pounded into their present shape by true believers in industrial society’s growth-for-its-own-sake ideology, people are rather more likely to grasp the meaning of the words “too much.”

I’ve used examples from our own civilization because they’re familiar, but every civilization reshapes its urban environment in the shape of its own mental models, which then reinforce those models in the minds of the people who live in that environment.

As these people in turn shape that environment, the result is positive feedback: the mental models in question become more and more deeply entrenched in the built environment and thus also the collective conversation of the culture, and in both cases, they also become more elaborate and more extreme.

The history of architecture in the western world over the last few centuries is a great example of this latter: over that time, buildings became ever more completely defined by straight lines, flat surfaces, simple geometries, and hard boundaries between one space and another—and it’s hardly an accident that popular culture in urban communities has simplified in much the same way over that same timespan.

One way to understand this is to see a civilization as the working out in detail of some specific set of ideas about the world. At first those ideas are as inchoate as dream-images, barely grasped even by the keenest thinkers of the time.

Gradually, though, the ideas get worked out explicitly; conflicts among them are resolved or papered over in standardized ways; the original set of ideas becomes the core of a vast, ramifying architecture of thought which defines the universe to the inhabitants of that civilization.

Eventually, everything in the world of human experience is assigned some place in that architecture of thought; everything that can be hammered into harmony with the core set of ideas has its place in the system, while everything that can’t gets assigned the status of superstitious nonsense, or whatever other label the civilization likes to use for the realities it denies.

The further the civilization develops, though, the less it questions the validity of the basic ideas themselves, and the urban environment is a critical factor in making this happen.

By limiting, as far as possible, the experiences available to influential members of society to those that fit the established architecture of thought, urban living makes it much easier to confuse mental models with the universe those models claim to describe, and that confusion is essential if enough effort, enthusiasm, and passion are to be directed toward the process of elaborating those models to their furthest possible extent.

A branch of knowledge that has to keep on going back to revisit its first principles, after all, will never get far beyond them.

This is why philosophy, which is the science of first principles, doesn’t “progress” in the simpleminded sense of that word—Aristotle didn’t disprove Plato, nor did Nietzsche refute Schopenhauer, because each of these philosophers, like all others in that challenging field, returned to the realm of first principles from a different starting point and so offered a different account of the landscape.

Original philosophical inquiry thus plays a very large role in the intellectual life of every civilization early in the process of urbanization, since this helps elaborate the core ideas on which the civilization builds its vision of reality; once that process is more or less complete, though, philosophy turns into a recherché intellectual specialty or gets transformed into intellectual dogma.

Cities are thus the Petri dishes in which civilizations ripen their ideas to maturity—and like Petri dishes, they do this by excluding contaminating influences. It’s easy, from the perspective of a falling civilization like ours, to see this as a dreadful mistake, a withdrawal from contact with the real world in order to pursue an abstract vision of things increasingly detached from everything else.

That’s certainly one way to look at the matter, but there’s another side to it as well.

Civilizations are far and away the most spectacularly creative form of human society. Over the course of its thousand-year lifespan, the inhabitants of a civilization will create many orders of magnitude more of the products of culture—philosophical, scientific, and religious traditions, works of art and the traditions that produce and sustain them, and so on—than an equal number of people living in non-urban societies and experiencing the very sedate pace of cultural change already mentioned.

To borrow a metaphor from the plant world, non-urban societies are perennials, and civilizations are showy annuals that throw all their energy into the flowering process. Having flowered, civilizations then go to seed and die, while the perennial societies flower less spectacularly and remain green thereafter.

The feedback loop described above explains both the explosive creativity of civilizations and their equally explosive downfall. It’s precisely because civilizations free themselves from the corrective feedback of nature, and divert an ever larger portion of their inhabitants’ brainpower from the uses for which human brains were originally adapted by evolution, that they generate such torrents of creativity.

Equally, it’s precisely because they do these things that civilizations run off the rails into self-feeding delusion, lose the capacity to learn the lessons of failure or even notice that failure is taking place, and are destroyed by threats they’ve lost the capacity to notice, let alone overcome.

Meanwhile, other kinds of human societies move sedately along their own life cycles, and their creativity and their craziness—and they have both of these, of course, just as civilizations do—are kept within bounds by the enduring negative feedback loops of nature.

Which of these two options is better? That’s a question of value, not of fact, and so it has no one answer. Facts, to return to a point made in these posts several times, belong to the senses and the intellect, and they’re objective, at least to the extent that others can say, “yes, I see it too.”

Values, by contrast, are a matter of the heart and the will, and they’re subjective; to call something good or bad doesn’t state an objective fact about the thing being discussed. It always expresses a value judgment from some individual point of view.

You can’t say “x is better than y,” and mean anything by it, unless you’re willing to field such questions as “better by what criteria?” and “better for whom?”

Myself, I’m very fond of the benefits of civilization. I like hot running water, public libraries, the rule of law, and a great many other things that you get in civilizations and generally don’t get outside of them.

Of course that preference is profoundly shaped by the fact that I grew up in a civilization; if I’d happened to be the son of yak herders in central Asia or tribal horticulturalists in upland Papua New Guinea, I might well have a different opinion—and I might also have a different opinion even if I’d grown up in this civilization but had different needs and predilections.

Robert E. Howard, whose fiction launched the series of posts that finishes up this week, was a child of American civilization at its early twentieth century zenith, and he loathed civilization and all it stood for.

This is one of the two reasons that I think it’s a waste of time to get into arguments over whether civilization is a good thing.

The other reason is that neither my opinion nor yours, dear reader, nor the opinion of anybody else who might happen to want to fulminate on the internet about the virtues or vices of civilization, is worth two farts in an EF-5 tornado when it comes to the question of whether or not future civilizations will rise and fall on this planet after today’s industrial civilization completes the arc of its destiny.

Since the basic requirements of urban life first became available not long after the end of the last ice age, civilizations have risen wherever conditions favored them, cycled through their lifespans, and fell, and new civilizations rose again in the same places if the conditions remained favorable for that process.

Until the coming of the fossil fuel age, though, civilization was a localized thing, in a double sense. On the one hand, without the revolution in transport and military technology made possible by fossil fuels, any given civilization could only maintain control over a small portion of the planet’s surface for more than a fairly short time—thus as late as 1800, when the industrial revolution was already well under way, the civilized world was still divided into separate civilizations that each pursued its own very different ideas and values.

On the other hand, without the economic revolution made possible by fossil fuels, very large sections of the world were completely unsuited to civilized life, and remained outside the civilized world for all practical purposes.

As late as 1800, as a result, quite a bit of the world’s land surface was still inhabited by hunter-gatherers, nomadic pastoralists, and tribal horticulturalists who owed no allegiance to any urban power and had no interest in cities and their products at all—except for the nomadic pastoralists, that is, who occasionally liked to pillage one.

The world’s fossil fuel reserves aren’t renewable on any time scale that matters to human beings.

Since we’ve burnt all the easily accessible coal, oil, and natural gas on the planet, and are working our way through the stuff that’s difficult to get even with today’s baroque and energy-intensive technologies, the world’s first fossil-fueled human civilization is guaranteed to be its last as well.

That means that once the deindustrial dark age ahead of us is over, and conditions favorable for the revival of civilization recur here and there on various corners of the planet, it’s a safe bet that new civilizations will build atop the ruins we’ve left for them.

The energy resources they’ll have available to them, though, will be far less abundant and concentrated than the fossil fuels that gave industrial civilization its global reach.

With luck, and some hard work on the part of people living now, they may well inherit the information they need to make use of sun, wind, and other renewable energy resources in ways that the civilizations before ours didn’t know how to do.

As our present-day proponents of green energy are finding out the hard way just now, though, this doesn’t amount to the kind of energy necessary to maintain our kind of civilization.

I’ve argued elsewhere, especially in my book The Ecotechnic Future, that modern industrial society is simply the first, clumsiest, and most wasteful form of what might be called technic society, the subset of human societies that get a significant amount of their total energy from nonbiotic sources—that is, from something other than human and animal muscles fueled by the annual product of photosynthesis.

If that turns out to be correct, future civilizations that learn to use energy sparingly may be able to accomplish some of the things that we currently do by throwing energy around with wild abandon, and they may also learn how to do remarkable things that are completely beyond our grasp today.

Eventually there may be other global civilizations, following out their own unique sets of ideas about the world through the usual process of dramatic creativity followed by dramatic collapse.

That’s a long way off, though. As the first global civilization gives way to the first global dark age, my working guess is that civilization—that is to say, the patterns of human society necessary to support the concentration of population, wealth, and power in urban centers—is going to go away everywhere, or nearly everywhere, over the next one to three centuries.

A planet hammered by climate change, strewn with chemical and radioactive poisons, and swept by mass migrations is not a safe place for cities and the other amenities of civilized life.

As things calm down, say, half a millennium from now, a range of new civilizations will doubtless emerge in those parts of the planet that have suitable conditions for urban life, while human societies of other kinds will emerge everywhere else on the planet that human life is possible at all.

I realize that this is not exactly a welcome prospect for those people who’ve bought into industrial civilization’s overblown idea of its own universal importance. Those who believe devoutly that our society is the cutting edge of humanity’s future, destined to march on gloriously forever to the stars, will be as little pleased by the portrait of the future I’ve painted as their equal and opposite numbers, for whom our society is the end of history and must surely be annihilated, along with all seven billion of us, by some glorious cataclysm of the sort beloved by Hollywood scriptwriters.

Still, the universe is under no obligation to cater to anybody’s fantasies, you know.

That’s a lesson Robert E. Howard knew well and wove into the best of his fiction, the stories of Conan among them—and it’s a lesson worth learning now, at least for those who hope to have some influence over how the future affects them, their families, and their communities, in an age of decline and fall.

Image above: Solar-voltaic electric panels at dusk. From original article.

Solar photovoltaic (PV) systems generate "free" electricity from sunlight, but manufacturing them is an energy-intensive process.

It's generally assumed that it only takes a few years before solar panels have generated as much energy as it took to make them, resulting in very low greenhouse gas emissions compared to conventional grid electricity.

However, the studies upon which this assumption is based are written by a handful of researchers who arguably have a positive bias towards solar PV. A more critical analysis shows that the cumulative energy and CO2 balance of the industry is negative, meaning that solar PV has actually increased energy use and greenhouse gas emissions instead of lowering them.

This doesn't mean that the technology is useless. It's just that our approach is wrong. By carefully selecting the location of the manufacturing and the installation of solar panels, the potential of solar power could be huge. We have to rethink the way we use and produce solar energy systems on a global scale.

There's nothing but good news about solar energy these days. The average global price of PV panels has plummeted by more than 75% since 2008, and this trend is expected to continue in the coming years, though at a lower rate. [1-2]

According to the 2015 solar outlook by investment bank Deutsche Bank, solar systems will be at grid parity in up to 80% of the global market by the end of 2017, meaning that PV electricity will be cost-effective compared to electricity from the grid. [3-4]

Lower costs have spurred an increase in solar PV installments. According to the Renewables 2014 Global Status Report, a record of more than 39 gigawatt (GW) of solar PV capacity was added in 2013, which brings total (peak) capacity worldwide to 139 GW at the end of 2013. While this is not even enough to generate 1% of global electricity demand, the growth is impressive. Almost half of all PV capacity in operation today was added in the past two years (2012-2013). [5] In 2014, an estimated 45 GW was added, bringing the total to 184 GW. [6] [4].

Meanwhile, solar cells are becoming more energy efficient, and the same goes for the technology used to manufacture them. For example, the polysilicon content in solar cells -- the most energy-intensive component -- has come down to 5.5-6.0 grams per watt peak (g/wp), a number that will further decrease to 4.5-5.0 g/wp in 2017. [2]

Both trends have a positive effect on the sustainability of solar PV systems. According to the latest life cycle analyses, which measure the environmental impact of solar panels from production to decommission, greenhouse gas emissions have come down to around 30 grams of CO2-equivalents per kilwatt-hour of electricity generated (gCO2e/kWh), compared to 40-50 grams of CO2-equivalents ten years ago. [7-11] [12]

According to these numbers, electricity generated by photovoltaic systems is 15 times less carbon-intensive than electricity generated by a natural gas plant (450 gCO2e/kWh), and at least 30 times less carbon-intensive than electricity generated by a coal plant (+1,000 gCO2e/kWh). The most-cited energy payback times (EPBT) for solar PV systems are between one and two years. It seems that photovoltaic power, around since the 1970s, is finally ready to take over the role of fossil fuels.

Manufacturing has Moved to China

Unfortunately, a critical review of the PV solar industry paints a very different picture. Many commenters attribute the plummeting cost of solar PV to more efficient manufacturing processes and scale economies. However, if we look at the graph below, we see that the decline in costs accelerates sharply from 2009 onwards.

This acceleration has nothing to do with more efficient manufacturing processes or a technological breakthrough. Instead, it's the consequence of moving almost the entire PV manufacturing industry from western countries to Asian countries, where labour and energy are cheaper and where environmental restrictions are more loose.

Less than 10 years ago, almost all solar panels were produced in Europe, Japan, and the USA. In 2013, Asia accounted for 87% of global production (up from 85% in 2012), with China producing 67% of the world total (62% in 2012). Europe's share continued to fall, to 9% in 2013 (11% in 2012), while Japan's share remained at 5% and the US share was only 2.6%. [5]

Compared to Europe, Japan and the USA, the electric grid in China is about twice as carbon-intensive and about 50% less energy efficient. [13-15]

Because the manufacture of solar PV cells relies heavily on the use of electricity (for more than 95%) [16], this means that in spite of the lower prices and the increasing efficiency, the production of solar cells has become more energy-intensive, resulting in longer energy payback times and higher greenhouse gas emissions.

The geographical shift in manufacturing has made almost all life cycle analyses of solar PV panels obsolete, because they are based on a scenario of domestic manufacturing, either in Europe or in the United States.

LCA of Solar Panels Manufactured in China

We could find only one study that investigates the manufacturing of solar panels in China, and it's very recent. In 2014, a team of researchers performed a comparative life cycle analysis between domestic and overseas manufacturing scenarios, taking into account geographic diversity by utilizing localized inventory data for processes and materials. [13]

In the domestic manufacturing scenario, silicon PV modules (mono-si with 14% efficiency and multi-si with 13.2% efficiency) are made and installed in Spain. In the overseas manufacturing scenario, the panels are made in China and installed in Spain.

Compared to the domestic manufacturing scenario, the carbon footprint and the energy payback time are almost doubled in the overseas manufacturing scenario. The carbon footprint of the modules made in Spain (which has a cleaner grid than the average in Europe) is 37.3 and 31.8 gCO2e/kWh for mono-si and multi-si, respectively, while the energy payback times are 1.9 and 1.6 years.

However, for the modules made in China, the carbon footprint is 72.2 and 69.2 gCO2e/kWh for mono-si and multi-si, respectively, while the energy payback times are 2.4 and 2.3 years. [13]

At least as important as the place of manufacturing is the place of installation. Almost all LCAs -- including the one that deals with manufacturing in China -- assume a solar insolation of 1,700 kilowatt-hour per square meter per year (kWh/m2/yr), typical of Southern Europe and the southwestern USA. If solar modules manufactured in China are installed in Germany, then the carbon footprint increases to about 120 gCO2e/kWh for both mono- and multi-si -- which makes solar PV only 3.75 times less carbon-intensive than natural gas, not 15 times.

Considering that at the end of 2014, Germany had more solar PV installed than all Southern European nations combined, and twice as much as the entire United States, this number is not a worst-case scenario. It reflects the carbon intensity of most solar PV systems installed between 2009 and 2014. More critical researchers had already anticipated these results. A 2010 study refers to the 2008 consensus figure of 50 gCO2e/kWh mentioned above, and adds that "in less sunny locations, or in carbon-intensive economies, these emissions can be up to 2-4 times higher". [17]

Taking the more recent figure of 30 gCO2e/kWh as a starting point, which reflects improvements in solar cell and manufacturing efficiency, this would be 60-120 gCO2e/kWh, which corresponds neatly with the numbers of the 2014 study.

These results don't include the energy required to ship the solar panels from China to Europe. Transportation is usually ignored in LCAs of solar panels that assume domestic production, which would make comparisons difficult.

Furthermore, energy requirements for transportation are very case-specific. It should also be kept in mind that these results are based on a solar PV lifespan of 30 years. This might be over-optimistic, because the relocation of manufacturing to China has been associated with a decrease in the quality of PV solar panels. [18]

Research has shown that the percentage of defective or under-performing PV cells has risen substantially in recent years, which could have a negative influence on the lifespan of the average solar panel, decreasing its sustainability.

Energy Cannibalism

Solar PV electricity remains less carbon-intensive than conventional grid electricity, even when solar cells are manufactured in China and installed in countries with relatively low solar insolation. This seems to suggest that solar PV remains a good choice no matter where the panels are produced or installed.

However, if we take into account the growth of the industry, the energy and carbon balance can quickly turn negative. That's because at high growth rates, the energy and CO2 savings made by the cumulative installed capacity of solar PV systems can be cancelled out by the energy use and CO2 emissions from the production of new installed capacity. [16] [19-20]

A life cycle analysis that takes into account the growth rate of solar PV is called a "dynamic" life cycle analysis, as opposed to a "static" LCA, which looks only at an individual solar PV system. The two factors that determine the outcome of a dynamic life cycle analysis are the growth rate on the one hand, and the embodied energy and carbon of the PV system on the other hand. If the growth rate or the embodied energy or carbon increases, so does the "erosion" or "cannibalization" of the energy and CO2 savings made due to the production of newly installed capacity. [16]

For the deployment of solar PV systems to grow while remaining net greenhouse gas mitigators, they must grow at a rate slower than the inverse of their CO2 payback time. [19]

For example, if the average energy and CO2 payback times of a solar PV system are four years and the industry grows at a rate of 25%, no net energy is produced and no greenhouse gas emissions are offset. [19]

If the growth rate is higher than 25%, the aggregate of solar PV systems actually becomes a net CO2 and energy sink. In this scenario, the industry expands so fast that the energy savings and GHG emissions prevented by solar PV systems are negated to fabricate the next wave of solar PV systems. [20]

The CO2 Balance of Solar PV

Several studies have undertaken a dynamic life cycle analysis of renewable energy technologies. The results -- which are valid for the period between 1998 and 2008 -- are very sobering for those that have put their hopes on the carbon mitigation potential of solar PV power. A 2009 paper, which takes into account the geographical distribution of global solar PV installations, sets the maximum sustainable annual growth rate at 23%, while the actual average annual growth rate of solar PV between 1998 and 2008 was 40%. [16] [21]

This means that the net CO2 balance of solar PV was negative for the period 1998-2008. Solar PV power was growing too fast to be sustainable, and the aggregate of solar panels actually increased GHG emissions and energy use. According to the paper, the net CO2 emissions of the solar PV industry during those 10 years accounted to 800,000 tonnes of CO2. [16] These figures take into account the fact that, as a consequence of a cleaner grid and better manufacturing processes, the production of solar PV panels becomes more energy efficient and less carbon-intensive over time.

The sustainability of solar PV has further deteriorated since 2008. On the one hand, industry growth rates have accelerated. Solar PV grew on average by 59% per year between 2008 and 2014, compared to an annual growth rate of 40% between 1998 and 2008 . [5] On the other hand, manufacturing has become more carbon-intensive. For its calculations of the CO2 balance in 2008, the study discussed above considers the carbon intensity of production worldwide to be 500 gCO2e/kWh. In 2013, with 87% of the production in Asia, this number had risen to about 950 gCO2e/kWh, which halves the maximum sustainable growth rate to about 12%.

If we also take into account the changes in geographic distribution of solar panels, with an increasing percentage installed in regions with higher solar insolation, the maximum sustainable growth rate increases to about 16%. [23-24] Although more recent research is not available, it's obvious that the CO2 emissions of the solar PV industry have further increased during the period 2009-2014. If we would consider all solar panels in the world as one large energy generating plant, it would not have generated any net energy or CO2-savings.

The Solution: Rethink the Manufacture and Use of Solar PV

Obviously, the net CO2 balance of solar PV could be improved by limiting the growth of the industry, but that would be undesirable. If we want solar PV to become important, it has to grow fast. Therefore, it's much more interesting to focus on lowering the embodied energy of solar PV power systems, which automatically results in higher sustainable growth rates. The shorter the energy and CO2 payback times, the faster the industry can grow without becoming a net producer of CO2.

Embodied energy and CO2 will gradually decrease because of technological advances such as higher solar cell efficiencies and more efficient manufacturing techniques, and also as a consequence of the recycling of solar panels, which is not yet a reality.

However, what matters most is where solar panels are manufactured, and where they are installed. The location of production and installation is a decisive factor because there are three parameters in a life cycle analysis that are location dependent: the carbon intensity of the electricity used in production, the carbon intensity of the displaced electricity mix at the place of installation, and the solar insolation in the place of installation. [16]

By carefully selecting the locations for production and installation we could improve the sustainability of solar PV power in a spectacular way. For PV modules produced in countries with low-carbon energy grids -- such as France, Norway, Canada or Belgium -- and installed in countries with high insolation and carbon-intensive grids -- such as China, India, the Middle East or Australia -- greenhouse gas emissions can be as low as 6-9 gCO2/kWh of generated electricity. [16] [20] [14-15] That's 13 to 20 times less CO2 per kWh than solar PV cells manufactured in China and installed in Germany. [25]

Sustainable growth rates of 300-460% are possible when PV modules are produced in countries with low-carbon energy grids and installed in countries with high insolation and carbon-intensive grids

This would allow sustainable growth rates of up to 300-460%, far above what's even necessary. If solar PV would grow on average at a rate of 100% per year, it would take less than 10 years to meet today's electricity's demand. If it would grow at the 16% maximum sustainable growth rate we calculated above, meeting today's electricity demand would take until 2045 -- with no net CO2 savings. By that time, according to the forecasts, total global electricity demand will have more than doubled. [26]

Of course, producing and installing solar panels in the right places implies international cooperation and a sound economic system, none of which exist. Manufacturing solar panels in Europe or the USA would also make them more expensive again, while many countries with the right conditions for solar don't have the money to install them in large amounts.

An alternative solution is using on-site generation from renewables to meet a greater proportion of the electricity demand of PV manufacturing facilities -- which can also happen in a country with a carbon-intensive grid. For example, if the electricity for the manufacturing of solar cells would be supplied by other solar cells, then the greenhouse emissions of solar PV systems could be reduced by 50-70%, depending on where they are produced (Europe or the USA). [7] In China, this decrease in CO2 emissions would even be greater.

In yet another scenario, we could dedicate nuclear plants exclusively to the manufacture of solar cells. Because nuclear is less carbon-intensive than PV solar, this sounds like the fastest, cheapest and easiest way to start producing a massive amount of solar cells without raising energy use and greenhouse emissions.

But don't underestimate the task ahead. A 1 GW nuclear power plant can produce about 11 million square metres of solar panels per year, which corresponds to 1.66 GWp of solar power (based on the often cited average number of 150 w/m2). We would have needed 24 nuclear plants -- or 1 in 20 atomic plants worldwide -- working full-time to produce the solar panels manufactured in 2013. [27]

What About Storage?

Why does the production of solar PV requires so much energy? Because the low power density -- several orders of magnitude below fossil fuels -- and the intermittency of solar power require a much larger energy infrastructure than fossil fuels do.

It's important to realize that the intermittency of solar power is not taken into account in our analysis. Solar power is not always available, which means that we need a backup-source of power or a storage system to jump in when the need is there.

This component is usually not considered in LCAs of solar PV, even though it has a large influence on the sustainability of solar power.

Storage is no longer an academic question because several manufacturers -- most notably Tesla -- are pushing lithium-ion battery storage as an alternative for a grid-connected solar PV system.
Lithium-ion batteries are more compact and technically superior to the lead-acid batteries commonly used in off-grid solar systems. Furthermore, the disincentivation of grid-connected solar systems in a growing number of countries makes off-grid systems more attractive.

In the next article, we investigate the sustainability of a PV-system with a lithium-ion battery. Meanwhile, enjoy the sun and stay tuned.

One of the constraints of solar power is that it is not always available: it is dependent on daylight hours and clear skies. In order to fill these gaps, a storage solution or a backup infrastructure of fossil fuel power plants is required -- a factor that is often ignored when scientists investigate the sustainability of PV systems.

Whether or not to include storage is no longer just an academic question. Driven by better battery technology and the disincentivization of grid-connected solar panels, off-grid solar is about to make a comeback. How sustainable is a solar PV system if energy storage is taken into account?

In the previous article, we have seen that many life cycle analyses (LCAs) of solar PV systems have a positive bias. Most LCAs base their studies on the manufacturing of solar cells in Europe or the USA. However, most panels are now produced in China, where the electric grid is about twice as carbon-intensive and about 50% less energy efficient. [1] Likewise, most LCAs investigate solar PV systems in regions with a solar insolation typical of the Mediterranean region, while the majority of solar panels have been installed in places with only half as much sunshine.

As a consequence, the embodied greenhouse gas emissions of a kWh of electricity generated by solar PV is two to four times higher than most LCAs indicate. Instead of the oft-cited 30-50 grams of CO2-equivalents per kilowatt-hour of generated electricity (gCO2e/kWh), we calculated that the typical solar PV system installed between 2008 and 2014 produces close to 120 gCO2e/kWh. This makes solar PV only four times less carbon-intensive than conventional grid electricity in most western countries.

However, even this result is overly optimistic. In the previous article, we didn't take into account "one of the potentially largest missing components" [2] of the usual life cycle analysis of PV systems: the embodied energy of the infrastructure that deals with the intermittency of solar power. Solar insolation varies throughout the day and throughout the season, and of course solar energy is not available after sunset.

Off-grid Solar Power is Back

Until the end of the 1990s, most solar installations were off-grid systems. Excess power during the day was stored in an on-site bank of lead-acid batteries for use during the night and on cloudy days. Today, almost all solar systems are grid-connected. These installations use the grid as if it was a battery, "storing" excess energy during the day for use at night and on cloudy days.

Obviously, this strategy requires a backup of fossil fuel or nuclear power plants that step in when the supply of solar energy is low or nonexistent. To make a fair comparison with conventional grid electricity, including electricity generated by biomass, this "hidden" part of the solar PV system should also be taken into account. However, every single life cycle analyse of a solar PV ignores it. [3, 2].

Until now, whether or not to include backup power or storage systems was mainly an academic question. This might change soon, because off-grid solar is about to make a comeback. Several manufacturers have presented storage systems based on lithium-ion batteries, the technology that also powers our gadgets and electric cars. [4, 5, 6, 7] Lithium-ion batteries are a superior technology compared to the lead-acid batteries commonly used in off-grid solar PV systems: they last longer, are more compact, more efficient, easier to maintain, and comparatively more sustainable.

Lithium-ion batteries are more expensive than lead-acid batteries, but Morgan Stanley's 2014 report on solar energy predicts that the price of storage will come down to $125-$150 per kWh by 2020. [8] According to the report, this would make solar PV plus battery storage commercially viable in some European countries (Germany, Italy, Portugal, Spain) and across most of the United States. Morgan Stanley expects a lot from electric vehicle manufacturer Tesla, who announced a home storage system for solar power a few days ago (costing $350 per kWh). [9] Tesla is building a factory in Arizona that will produce as many lithium-ion batteries as there are currently produced by all manufacturers in the world, introducing economies of scale that can push costs further down.

Other factors also come into play when it comes to home storage for PV power. Solar panels have become so much cheaper in recent years that government subsidies and tax credits for grid-connected systems have come under pressure. In many countries, owners of a grid-connected solar PV system have received a fixed price for the surplus electricity they provide to the grid, without having to pay fixed grid rates. These so-called "net metering rules" or "feed-in rates" were recently abolished in several European countries, and are now under pressure in some US states. In its report, Morgan Stanley predicts that, in the coming years, net metering rules and solar tax credits will disappear altogether. [8]

Utility companies are fighting the incentivisation of PV power succesfully with the argument that solar customers make use of the grid but don't pay for it, raising the costs for non-solar customers. [10] The irony is that the disincentivization of grid-connected solar panels makes off-grid systems more attractive, and that utilities might be chasing away their customers.

If a grid-connected solar customer has to pay fixed grid fees and doesn't receive a good price for his or her excess power, it might become more financially savvy to install a bank of batteries. The more customers do this, the higher the costs will become for the remaining consumers, encouraging more people to adopt off-grid systems. [11]

Lead-Acid Battery Storage

Being totally independent of the grid might sound attractive to many, but how sustainable is a solar PV system when battery storage is taken into account? Because a life cycle analysis of an off-grid solar system with lithium-ion batteries has not yet been done, we made one ourselves, based on some LCAs of stand-alone solar PV systems with lead-acid battery storage.

One of the most complete studies to date is a 2009 LCA of a 4.2 kW off-grid system in Murcia, Spain. The 35 m2 PV solar array is mounted on a building rooftop and supplies a programmed lighting system with a daily constant load pattern of 13.8 kWh.

The solar panels are connected to 24 open lead-acid batteries with a storage capacity of 110.4 kWh, offering three days of autonomy. [12] The study found an energy payback time of 9.08 years and specific greenhouse gas emissions of 131 gCO2e/kWh, which makes the system twice as energy efficient and 2.5 times less carbon-intensive than conventional grid electricity in Spain (337 gCO2/kWh). Manufacturing the batteries accounts for 45% of the embodied CO2, and 49% of the life cycle energy use of the solar system.

This doesn't sound too bad, but unfortunately the researchers made some pretty optimistic assumptions. First of all, the results are valid for a solar insolation of 1,932 kWh/m2/yr -- Murcia is one of the sunniest places in Spain. At lower solar insolation, more solar panels would be needed to produce as much electricity, so the embodied energy of the total system will increase. [13]. If we assume a solar insolation of 1,700 kWh/m2/yr, the average in Southern Europe, GHG emissions would increase to 139 gCO2e/kWh. If we assume a solar insolation of 1,000 kWh/m2/yr, the average in Germany, emissions amount to 174 gCO2/kWh.

Battery Lifespan

Secondly, the researchers assume the lifespan of the lead-acid batteries to be 10 years. For the solar panels, they assume a lifetime of 20 years, which means that they included double the amount of batteries in the life cycle analysis. A lifespan of ten years is very optimistic for a lead-acid battery -- a fact that the scientists admit. [12] Most other LCA's looking at off-grid systems assume a battery life of 3 or 5 years [14, 15]. However, the lifetime of a lead-acid battery depends strongly on use and maintenance. Because of the low load of the system under discussion, a battery lifespan of 10 years is not completely unrealistic.

On the other hand, if the batteries are used for higher loads -- for example, in a common household -- their lifetime would shorten considerably. Because almost 50% of embodied CO2 and life cycle energy use of a PV solar system is due to the batteries alone, the expected lifespan of the 2.4 ton battery pack has a profound effect on the sustainability of the system.

If we assume a battery lifespan of 5 instead of 10 years, and keep the other parameters the same, the GHG emissions increase to 198 and 233 gCO2e/kWh for a solar insolation of 1,700 and 1,000 kWh/m2/yr, respectively. In grid-connected solar PV systems, assuming a longer life expectancy for the solar panels improves the sustainability of the system: the embodied energy and CO2 can be spread over a longer period of time. With off-grid systems, this effect is countered by the need for one or more replacements of the batteries.

If we increase the life expectancy of the solar panels from 20 to 30 years, and keep the battery lifespan at 10 years, CO2e emissions per kWh remain more or less the same. However, if we assume a battery lifespan of only 5 years and extend the lifespan of the solar panels to 30 years, GHG emissions would increase to 206 gCO2e/kWh for a solar insolation of 1,700 kWh/m2/yr, and decrease to 232 gCO2e/kWh for a solar insolation of 1,000 kWh/m2/yr.

Made in China

Thirdly, the researchers assume that all components -- PV cells, batteries, electronics -- are made in Spain, while we have seen in the previous article that manufacturing of solar PV systems has moved to China. Spain's electricity grid is 2.7 times less carbon-intensive (337 gCO2/kWh) than China's electric infrastructure (900 gCO2e/kWh), which means that the GHG emissions of all components of our system can be multiplied by 2.7.

This results in specific carbon emissions of 353 and 471 gCO2e/kWh for a solar insolation of 1,700 and 1,000 kWh/m2/yr, respectively, which is higher than the carbon-intensity of the Spanish grid. Considering a battery lifespan of 5 instead of 10 years, emissions would rise to 513 and 631 gCO2e/kWh for a solar insolation of 1,700 and 1,000 kWh/m2/yr, respectively.

Although there are some assumptions by the researchers that are less optimistic -- such as a battery recycling rate of only 50% instead of the more commonly assumed +90% -- it's obvious that an off-grid system with lead-acid batteries is not sustainable, and definitely not when the components are manufactured in China. That doesn't make off-grid solar with lead-acid batteries pointless: compared to a diesel generator, a solar PV system with lead-acid batteries is often the better choice, which makes it a good solution for remote areas without access to the power grid. As an alternative for the centralized electricity infrastructure in western countries, however, it makes little sense.

Lithium-ion Battery Storage System

When we replace the lead-acid batteries by lithium-ion batteries, the sustainability of a stand-alone solar PV system improves considerably. At first glance this may seem counter-productive, because it takes more energy to produce 1 kWh of lithium-ion battery storage than it takes to manufacure 1 kWh of lead-acid battery storage. According to the latest LCA's, aimed at electric vehicle storage, the making of a lithium-ion battery requires between 1.4 and 1.87 MJ/wh, [16, 17, 18] while the energy requirements for the manufacture of a lead-acid battery are between 0.87 and 1.19 MJ/Wh. [18, 12]

Despite this, the higher overall performance of the lithium-ion battery means that considerably less storage is required. For a prolonged lifetime, lead-acid batteries demand a limited "Depth of Discharge" (DoD). If a lead-acid battery is fully discharged (DoD of 100%) its lifespan becomes very short (300 to 800 cycles, or roughly one to two years, depending on battery chemistry).

he lifespan increases to between 400 and 1,000 cycles (1-3 years, assuming 365 cycles per year) at a DoD of 80%, and to between 900 and 2,000 cycles (2.5-5.5 years) at a DoD of 33%. [18]. This means that, in order to get a decent lifespan, a lead-acid battery system should be oversized. For example, three times more battery capacity is needed at a DoD of 33%, because two thirds of the battery capacity cannot be used.

Although the lifespan of a lithium-ion battery also decreases when the depth of discharge increases, this effect is less pronounced than with its lead-acid counterpart. A lithium-ion battery lasts 3,000 to 5,000 cycles (8-14 years) at a DoD of 100%, 5,000 to 7,000 cycles (14-19 years) at a DoD of 80%, and 7,000 to 10,000 cycles (19-27 years) at a DoD of 33%. [18]

As a consequence, lithium-ion storage usually has a DoD of 80%, while lead-acid storage usually has a DoD of 33 or 50%. In the LCA of the Spanish off-grid system discussed above, the assumption of three days of autonomy implies that 41 kWh of storage is required (3 x 13.8 kWh per day). Because the DoD is 33%, total storage capacity should be multiplied by three, which results in 123 kWh of batteries. If we would replace these by lithium-ion batteries with a DoD of 80%, only 50 kWh of storage is needed, or 2.5 times less.

6 x Less Batteries Needed

For utmost accuracy, we should mention that the lifespan of a battery isn't necessarily limited by the cycle life. When batteries are used in applications with shallow cycling, their service life will normally be limited by float life. In this case, the difference between lead-acid and lithium-ion is less pronounced: at no-cycling (float charge), lithium-ion lasts 14-16 years and lead-acid 8-12 years.

Battery life will be limited by either the life cycle or the float service life, depending on which condition will be achieved first. [18] Nevertheless, if we focus on off-grid systems for households, the assumption of deep daily cycling better reflects reality, although there will be periods of float charge, for example during holidays.

If we also factor in the lifespan of the batteries, the advantage of lithium-ion becomes even larger. Assuming a lifespan of 20 years for the solar PV system and a DoD of 80%, the lithium-ion batteries will last as long as the PV panels. On the other hand, the lead-acid batteries have to be replaced at least 2-4 times over a period of 20 years. This further widens the gap in energy use for manufacturing when comparing lead-acid and lithium-ion batteries. [18]

In the original LCA, a total storage capacity of about 240 kWh is needed over a lifespan of 20 years. On the other hand, the cycle life of the lithium-ion battery is 19-27 years, meaning that no replacement may be needed. Consequently, the total storage capacity to be manufactured over the complete lifetime of the system is 6 times lower for lithium-ion than for lead-acid. [19]

If we take the most optimistic values for energy during manufacturing, being 0.87 MJ/Wh for lead-acid and 1.4 MJ/Wh for lithium-ion, and multiply them by total battery capacity over a lifetime of 20 years (248,000 Wh for lead-acid and 42,000 Wh for lithium-ion), this results in an embodied energy of 60 MWh for lead-acid (the value in the original LCA) and only 16.5 MWh for lithium. In conclusion, energy requirements for the manufacturing of the batteries is 3.6 times lower for lithium-ion than for lead-acid.

Another advantage of lithium-ion batteries is that they have a higher efficiency than lead-acid batteries: 85-95% for lithium-ion, compared to 70-85% for lead-acid. Because losses in the battery must be compensated with higher energy input, a higher battery efficiency results in a smaller PV array, lowering the energy requirements to manufacture the solar cells. In the original LCA, 4.2 kW of solar panels (35 m2) are needed to produce 13.8 kWh per day.

If we assume the lead-acid batteries to be 77% efficient, and the lithium-ion batteries to be 90% efficient, the choice for lithium-ion would resize the solar PV array from 4.2 kW to 3.55 kW. We now have all the data to calculate the greenhouse gas emissions per kWh of electricity produced by an off-grid solar PV system using lithium-ion batteries.

GHG Emissions of the Off-grid System with Lithium-ion Batteries

In the original LCA, the batteries and the solar panels (including frames and supports) account for 59 and 62 gCO2e/kWh, respectively. The rest of the components add another 10 gCO2e/kWh, resulting in a total of 131 gCO2e/kWh. If we switch to lithium-ion battery storage, the greenhouse gas emissions for the batteries come down from 59 to 20 gCO2e/kWh.

Because of the higher efficiency of the lithium-ion batteries, the greenhouse gas emissions for the solar panels come down from 62 to 55 gCO2e/kWh. This brings the total greenhouse gas emissions of the off-grid system using lithium-ion batteries to 85 gCO2e/kWh, compared to 131 gCO2e/kWh for a similar system with lead-acid storage.

While this result is an improvement, it's dependent on the assumptions of the researchers; most notably, a solar insolation of 1,932 kWh/m2/yr, and that all manufacturing of components occurs in Spain. If we adjust the value for a solar insolation of 1,700 kWh/m2/yr in order to compare with the other results, total GHG emissions become 92.5 gCO2e/kWh (assuming battery capacity remains the same).

If we correct for a solar insolation of 1,000 kWh/m2/yr, the average in Germany, GHG emissions become 123.5 gCO2e/kWh. Furthermore, if we assume that the solar panels (but not the batteries or the other components) are manufactured in China, which is most likely the case, GHG emissions rise to 155 and 217 gCO2e/kWh for a solar insolation of 1,700 and 1,000 kWh/m2/yr, respectively.

In conclusion, lithium-ion battery storage makes off-grid solar PV less carbon-intensive than conventional grid electricity in most western countries, even if the manufacturing of solar panels in China is taken into account. However, the advantage is rather small, which effects the speed at which solar PV systems can be deployed in a sustainable way.

In the previous article, we have seen that the energy and CO2 savings made by the cumulative installed capacity of solar PV systems are cancelled out to some extent by the energy use and CO2 emissions from the production of new installed capacity. For the deployment of solar systems to grow while remaining net greenhouse gas mitigators, they must grow at a rate slower than the inverse of their CO2 payback time. [20, 21, 22]

For solar panels manufactured in China and installed in countries like Germany, the maximum sustainable growth rate is only 16-23% (depending on solar insolation), roughly 3 times lower than the actual annual growth of the industry between 2008 and 2014. If we also take lithium-ion battery storage into account, the maximum sustainable growth rate comes down to 4-14%.

In other words, including energy storage further limits the maximum sustainable growth rate of the solar PV industry.

On the other hand, if we would produce solar panels in countries with very clean electricity grids (France, Canada, etc.) and install them in countries with carbon-intensive grids and high solar insolation (China, Australia, etc.), even off-grid systems with lithium-ion batteries would have GHG emissions of only 26-29 gCO2/kWh, which would allow solar PV to grow sustainably by almost 60% per year. This result is remarkable and shows the importance of location if we want solar PV to be a solution instead of a problem. Of course, whether or not there's enough lithium available to deploy battery storage on a large scale, is another question.

Battery Production Powered by Renewable Energy?

Another way to improve the sustainability of battery storage is to produce the batteries using renewable energy. For example, Tesla announced that its "GigaFactory", which will produce lithium-ion batteries for vehicles and home storage, will be powered by renewable energy. [23, 24]

To support their claim, Tesla published an illustration of the factory with the roof covered in solar panels and a few dozen windmills in the distance.

However, the final manufacturing process in the factory consumes only a small portion of the total energy cost of the entire production cycle -- much more energy is used during material extraction (mining). It's stated that the GigaFactory will produce 50 GWh of battery capacity per year by 2020.

Because the making of 1 kWh of lithium-ion battery storage requires 400 kWh of energy [16, 17, 18], producing 50 GWh of batteries would require 20,000 GWh of energy per year.

If we assume an average solar insolation of 2,000 kWh/m2/yr and a solar PV efficiency of 15%, one m2 of solar panels would generate at most 295 kWh per year. This means that it would take 6,800 hectares (ha) of solar panels to run the complete production process of the batteries on solar power, while the solar panels on the roof cover an area of only 1 to 40 ha (there is some controversy over the actual surface area of the factory under construction). Tesla's claim, though potentially factually accurate, is an obvious example of greenwashing -- and everyone seems to buy it.

There are other ways to improve the sustainability of solar PV when storage is taken into account. Most of these solutions require that solar systems remain connected to the grid, even if they have a (more limited) local storage system. In this scenario, chemical batteries could help to balance the grid system, acting as peak-shaving and load-shifting devices. The electric grid has to be sized to meet peak demand, and battery storage could mean that less power plants are needed for that.

Decentralized, grid-connected energy storage could also increase the share of renewables that the electricity infrastructure can handle. Of course, this "smart grid" approach should also be subjected to a life cycle analysis, including all electronic components.